1. Field of the Invention
Aspects of the present invention generally relate to a secondary battery.
2. Description of the Related Art
Owing to various advantages, including a high operating voltage and high energy density per unit weight, lithium ion secondary batteries are used as power sources for portable electronic devices as well as motor-driving power source for hybrid electric vehicles.
The above information disclosed in this Related Art section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.